title: Mutagenesis study of the glycosylphosphatidylinositol phospholipase C of Trypanosoma brucei.
abstract: The glycosylphosphatidylinositol phospholipase C (GPI-PLC) from Trypanosoma brucei is particularly effective in hydrolysing the GPI-anchors of some proteins. The enzyme is inhibited by Zn2+ and p-chloromercurylphenylsulphonic acid, both of which can act as sulphydryl reagents, suggesting that a cysteine residue may be important in catalysis. Single cysteine to serine mutants have been produced for all eight cysteines in GPI-PLC; all the mutants were fully active in vitro and were still susceptible to p-chloromercurylphenylsulphonic acid inhibition. In contrast, a single histidine 34 to glutamine mutation totally inactivated GPI-PLC. The histidine was chosen after a sequence alignment with the Bacillus cereus phosphatidylinositol phospholipase C (PI-PLC) suggested a conservation of active site residues, including histidine 34 which is central to the proposed reaction mechanism (Heinz D.W., Ryan M., Bullock T.L., Griffith O.H. EMBO J 1995;14:3855-3863). The results suggest that the GPI-PLC and bacterial PI-PLCs have conserved active sites and that the inhibition of GPI-PLC by sulphydryl reagents can occur through more than one residue.
authors.affiliation: Department of Biochemistry, Cambridge, UK.
authors.forename: N
authors.initials: N
authors.lastname: Carnall
authors.forename: H
authors.initials: H
authors.lastname: Webb
authors.forename: M
authors.initials: M
authors.lastname: Carrington
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001409:Bacillus cereus / Q000201:enzymology / Q000235:genetics; D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D054800:Glycosylphosphatidylinositol Diacylglycerol-Lyase; D006639:Histidine / Q000737:chemistry; D008089:Listeria monocytogenes / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D013439:Sulfhydryl Reagents; D006639:Histidine; D002731:4-Chloromercuribenzenesulfonate; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054800:Glycosylphosphatidylinositol Diacylglycerol-Lyase; D003545:Cysteine